3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
The obtained dependence can be effectively used as calibration
curve enabling the estimation of previously absorbed
dose. 5,9–11
Relative radical content, a.u.
1.00
0.75
0.50
0.25
0.00
2 34 61 98 128 190
Time after γ-irradiation, day
Semiquinones
Carbohydrates I
Carbohydrates II
Carbohydrates III
Carbohydrates IV
Fig. 2. The dependence of relative radicals’ content on time
after the γ-irradiation obtained from the simulation analysis of
experimental EPR spectra of caraway sample treated at dose of
30 kGy
Relative ABTS •+ concentration, a. u.
1.00
0.75
0.50
0.25
0.00
4 HN 3 OS
CH 2 CH 3
CH 2 CH 3
S
N N
S
3 6 9 12 15 18
Time after ABTS •+ addition, min
SO 3 NH 4
Reference
0 kGy
5 kGy
10 kGy
20 kGy
30 kGy
Fig. 3. The dependence of relative AbTS •+ concentration on
time after its mixing with caraway ethanolic extracts prepared
from samples exposed to different doses of γ-radiation. Inset
represents the structural formula of AbTS. Extracts were prepared
2 days after the irradiation. Pure ethanol was used as reference
As a result of irreversible decay of radical structures
induced by γ-radiation, the integral EPR spectra intensity
of irradiated samples decreased gradually as is clearly
demonstrated on Fig. 1. and Fig. 2. for caraway samples. On
the contrary, the signal intensity of both reference samples
remains practically unchanged.
s562
Detail evaluation of experimental spectra revealed the
lowest stability of cellulosic radicals in laurel leaves (half life
∼ 10 weeks) followed by carbohydrate radicals, which stability
ranged from 20 up to 60 weeks. These results are in good
agreement with our previously published papers. 5,9–11
Ethanolic extracts of both reference spices revealed significant
ability to terminate • DPPH as well as ABTS •+ radicals.
As demonstrated on Fig. 3., it is only slightly influenced
by the absorption of γ-radiation. Results obtained moreover
showed, that radical-scavenging ability of laurel leaves’
extracts is significantly higher than that of caraway; probably
due to the differences in types and concentrations of polyphenolic
compounds.
UV-VIS experiments proved, that radiation treatment
resulted in significantly increased • DPPH radical-scavenging
activity of bay leaves methanolic extracts. In addition, the
TBARS value of caraway extracts, representing a measure of
oxidative products concentration, was slightly increased. As
a result of post-irradiation storage, a minor increase of ferric
reducing power, • DPPH radical-scavenging ability as well as
content of polyphenolic compounds of bay leaves extracts
was noticed, whereas the TBARS values of both, caraway
and bay leaves extracts, was somewhat reduced.
Discriminant analysis of all variables obtained from UV-
VIS experiments was used to differentiate the studied spices
according to the absorbed dose. As depicted on Fig. 4., the
effective discrimination was achieved only when non-irradiated
samples and samples treated by dose of 30 kGy were
compared. Using this approach, 93% correctness of caraway
classification was found, influenced mostly by TBARS values
and TPC content. In the case of bay leaves, 73% correct differentiation
of non-irradiated sample from sample γ-irradiated
at 30 kGy was found.
Fig. 4. Canonical discriminant analysis of non-irradiated
caraway samples (C0) and of samples γ-irradiated at 30 kGy
(C30). Characteristics obtained from uV-VIS experiments
( • DPPh, TbARS, FRP, TPC) immediately after the irradiation
and during the storage of samples at ambient conditions were
used as variables